KR101632441B1 - Method of refining carbon parts for production of polycrystalline silicon - Google Patents

Abstract

The method for purifying a carbon part for producing a polycrystalline silicon is characterized in that a carbon part used for producing polycrystalline silicon is accommodated in a processing furnace and the interior of the processing furnace is replaced with an inert gas or the like, (Step 2) of circulating the chlorine gas in the treatment furnace while raising the temperature of the treatment furnace to a purification temperature higher than the drying temperature after the drying treatment, and a chlorination treatment (Step 3) of decompressing the inside of the processing furnace after the processing, a decompression maintaining processing (step 4) of maintaining the processing furnace in the decompressed state caused by the decompression processing, and a chlorine gas introducing step And the chlorine pressurizing treatment (Step 5) for pressurizing the inside of the treatment furnace is repeated a plurality of times, and then the inside of the treatment furnace is cooled.

Polycrystalline silicon, carbon parts, refining, chlorine pressure treatment, silicon mandrel

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for purifying carbon parts for producing polycrystalline silicon,

The present invention relates to a method for purifying unused carbon parts and used carbon parts used in the production of polycrystalline silicon.

Priority is claimed on Japanese Patent Application No. 2008-236178, filed on September 16, 2008, the contents of which are incorporated herein by reference.

As a polycrystalline silicon production apparatus, a production apparatus by the Siemens method is known. In this apparatus for producing polycrystalline silicon, a plurality of silicon core rods are arranged in the reaction furnace. The silicon core in the reaction furnace is heated, and a raw material gas containing a mixed gas of chlorosilane gas and hydrogen gas is supplied to the reaction furnace to be brought into contact with the silicon mandrel. Then, polycrystalline silicon is deposited on the surface of the silicon core rod by hydrogen reduction reaction of the raw material gas and pyrolysis reaction.

Electrodes, heaters, etc. used in this reaction furnace are made of carbon so as not to contaminate the silicon. In the production of silicon for semiconductor, particularly high purity is required. For this reason, refining of carbon parts is carried out prior to use. In the case of purifying this carbon part, for example, in the method disclosed in Japanese Patent Publication No. 2649166, carbon parts are accommodated in a flow-through type reactor and chlorine gas is circulated at 800 to 1100 ° C for 10 to 30 hours, Thereby removing impurities therein. Further, the method disclosed in Japanese Patent Publication No. 39-12246 is a method for reducing phosphorus in carbon by continuously performing heat treatment for at least 100 hours by using exhaust gas at the time of producing polycrystalline silicon.

In the method disclosed in Japanese Patent Publication No. 1-40000, a carbon part is contained in a reaction furnace, and the inside of the furnace is maintained at 1000 占 폚, and a gas containing halogen, for example, hydrogen chloride Treated for 4 hours in a reduced pressure state and further heat-treated for 5 hours in a reducing atmosphere such as a hydrogen atmosphere. The method disclosed in Japanese Patent Application Laid-Open No. 2004-2085 is a method in which halogen treatment is performed at a high temperature of 2400 to 3000 占 폚 for 20 hours, for example, and then cooled to 50 占 폚 in an inert gas atmosphere, In the method of reproducing used carbon parts, silicon attached to the carbon parts is removed for each carbon base material, and then heat treatment is performed in a chlorine gas atmosphere to reduce impurities and reuse.

As described above, various methods have been proposed as a method for purifying carbon parts. However, in order to remove impurities from the carbon parts, the impurities attached to the carbon parts are embedded not only on the surface but also on the surface thereof. There is a problem of poor productivity due to the necessity of a method of heat treatment for a long time in an atmosphere of chlorine gas or the like.

Further, as for the method of reusing the carbon parts, silicon is attached to the surface of the carbon parts at the time of producing the polycrystalline silicon, so that it is necessary to remove the silicon and purify the carbon parts after removing the silicon. Japanese Patent Publication No. 3654418 discloses that silicon adhering to the surface of a carbon component is shaved for each carbon member (base material). However, when the strength of a carbon component is lowered, a polycrystalline silicon rod is liable to collapse There is a possibility that the productivity is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to improve productivity by efficiently removing impurities in a short period of time without performing a continuous treatment at a high temperature for a long time at a carbon part used as a carbon part for producing polycrystalline silicon. Further, for used carbon parts, the silicon attached to the surface of the used carbon parts can be efficiently removed without affecting the quality and strength of the carbon parts, and the polycrystalline silicon having the quality of the semiconductor grade can be obtained without performing the heat treatment for a long time. And to provide a method for purifying a carbon part which can be obtained.

The purification method of the present invention is a method for purifying a carbon part for producing polycrystalline silicon, comprising the steps of: storing a carbon part (unused carbon part) used for producing polycrystalline silicon in a treatment furnace, replacing the inside of the treatment furnace with an inert gas or the like, A drying treatment for raising the inner temperature of the treatment furnace to a drying temperature and circulating an inert gas or the like to dry the carbon part; and a step for raising the temperature of the treatment furnace to a refining temperature higher than the above-mentioned drying temperature, A decompression maintaining process of maintaining the inside of the process furnace under a reduced pressure condition caused by the decompression process, and a decompression maintaining process of performing the decompression maintaining process in the decompression maintaining process after the chlorine circulation process, A chlorine pressurizing process for introducing chlorine gas to pressurize the interior of the processing furnace, And it characterized by.

That is, this purification method is a method in which an inert gas or the like is introduced into the treatment furnace to prevent the oxidation of the carbon parts or the furnace internal material at the time of temperature rise in the furnace, The temperature is raised to the drying temperature to dry off the water adsorbed on the carbon parts. If the drying is insufficient, chlorine gas and moisture react with each other due to the introduction of chlorine gas after drying, hydrochloric acid is generated, and hydrochloric acid corrodes the furnace material, thereby contaminating the carbon parts to be treated in the furnace . In order to prevent this, this drying needs to be carried out sufficiently. Thereafter, the temperature in the treatment furnace is raised to a refining temperature higher than the temperature at which the carbon parts are dried, chlorine gas is introduced, and impurity elements such as boron and phosphorus contained in the carbon parts are reacted with chlorine gas, Separate. Thereafter, the inside of the treatment furnace is depressurized to discharge the gas containing the impurities in the treatment furnace to the outside of the treatment furnace. Further, by maintaining the inside of the treatment furnace under a constant high-temperature and low-pressure after the pressure reduction treatment, the impurities in the carbon material are efficiently removed from the inside of the carbon part.

Next, chlorine gas is introduced into the treatment furnace up to the pressurized state, so that chlorine gas penetrates into the interior of the carbon part to sufficiently react with the impurities in the carbon.

In the subsequent cooling step, the inside of the treatment furnace may be cooled while introducing chlorine gas until the drying temperature is reached and inert gas or the like is introduced at a temperature lower than the drying temperature. This is to prevent chlorine remaining in the furnace from reacting with moisture in the air when the carbon parts are taken out of the furnace, thereby preventing the furnace from being corroded.

In this case, the decompression holding treatment is preferably performed so that the inside of the treatment furnace is maintained at -0.02 MPa (G) or less and -0.1 MPa (G) or more in comparison with the atmospheric pressure, and the chlorine- (G) or more and 0.05 MPa (G) or less. The drying temperature is not lower than 350 ° C but not higher than 600 ° C, and the purifying temperature after drying the carbon parts may be not lower than 700 ° C and not higher than 1400 ° C.

Further, in the purification method of the present invention, the steps from the pressure reduction treatment to the chlorine pressure treatment may be repeated a plurality of times before the inside of the treatment furnace is cooled.

By repeating these series of treatments, the impurities contained in the carbon parts are efficiently separated and removed not only from the surface of the carbon parts but also from the interior thereof, without treatment in an atmosphere such as continuous chlorine gas or the like at a high temperature for a long time .

The purification method of the present invention is a method for purifying a carbon part after being used in the production of polycrystalline silicon. The method comprises the steps of accommodating a carbon part used for producing polycrystalline silicon in a processing furnace, replacing the inside of the processing furnace with an inert gas, The used carbon is subjected to drying treatment for drying the used carbon parts by raising the temperature to the silicon removal temperature while flowing inert gas or the like through the furnace, and after the used carbon is dried, the inside is decompressed A used chlorine pressurizing treatment for introducing chlorine gas into the treatment furnace after the decompression treatment for carbon which has been used and a treatment after the used chlorine pressurizing treatment for carbon are introduced into chlorine gas A pressure holding process for holding the pressure inside the processing furnace after the pressure holding process, A chlorine circulating process for circulating chlorine gas in the process furnace, a decompression process for decompressing the interior of the process chamber after the chlorine circulation process, a decompression maintaining process for maintaining the inside of the process chamber under the decompression process caused by the decompression process, , A chlorine pressurizing process for introducing chlorine gas into the process furnace after the decompression maintaining process to pressurize the inside of the process furnace, and then cooling the inside of the process furnace.

That is, in this refining method, an inert gas or the like is introduced into the treatment furnace, and the inside of the furnace is replaced with an inert gas or the like, thereby preventing the oxidation of the carbon parts and the furnace inside at the time of temperature rise in the furnace, Gas is circulated, the temperature in the furnace is raised to the silicon removal temperature, and moisture adsorbed on the carbon parts is sufficiently dried and removed. Thereafter, a decompression process for discharging the inert gas out of the system is performed. Thereafter, chlorine gas is introduced into the treatment furnace. The used carbon parts have silicon attached to the surface of the polycrystalline silicon deposition on its surface and react with the introduced chlorine gas to become silicon tetrachloride having a low boiling point. Thereafter, the chlorine gas is continuously introduced into the treatment furnace, and the carbon parts are uniformly and uniformly supplied to the carbon parts by the chlorine gas at a reaction equilibrium amount (an amount necessary for reaction with the silicon attached to the used carbon parts) The temperature is applied to the attached silicon so that the reaction with the chlorine gas is promoted efficiently without being subjected to the treatment by the chlorine gas circulation for a long time at a high temperature to be a low boiling point gas such as silicon tetrachloride to be separated and removed from the carbon part.

That is, the carbon part used for producing the polycrystalline silicon is chlorinated by reacting with chlorine gas in the means for removing silicon, and is then removed with silicon tetrachloride or the like having a low boiling point. In this treatment, for example, at a temperature of 600 ° C or higher, silicon may be formed by thermal decomposition of silicon tetrachloride or the like. Since silicon is adhered not only to the carbon parts but also to the furnace, It is preferable that the temperature is such that it is not pyrolyzed.

After the silicon on the surface of the carbon part is removed, impurities such as phosphorus attached to the surface and inside of the carbon part can be removed by performing a series of treatments in the same manner as the method of purifying the unused carbon part. As a result, the used carbon parts can be used for manufacturing polycrystalline silicon in the same manner as unused carbon parts.

In this case, the decompression treatment for the used carbon can be maintained at -0.02 MPa (G) or less and -0.1 MPa (G) or more in comparison with the atmospheric pressure in the treatment furnace. In the pressurization maintaining treatment with chlorine gas , The inner pressure may be pressurized to 0.01 MPa (G) or more and 0.05 MPa (G) or less in comparison with the atmospheric pressure by the treatment. The silicon removal temperature may be 350 to 600 占 폚. The purifying temperature may be 700 to 1400 ° C.

Further, in the refining method of the present invention, it may be necessary to repeat the steps from the decompression treatment for the carbon used to the pressurization and holding treatment for a plurality of times before the transition to the chlorine circulation treatment.

By repeating this series of processes, the silicon adhering to the carbon parts is reliably removed from the carbon parts, and the generated silicon tetrachloride is discharged from the treatment furnace.

In the refining method of the present invention, the inside of the processing furnace is cooled in the cooling step while the cooling step and the drying step are performed during the transition from the pressurized holding treatment to the chlorine circulation treatment. Thereafter, in the drying step, The inside of the furnace may be heated to a drying temperature, and an inert gas or the like may be circulated to dry the carbon parts.

In this case, the drying temperature may be 350 ° C or higher and 600 ° C or lower.

Further, in the purifying method of the present invention, the steps from the pressure reduction treatment to the chlorine pressure treatment may be repeated a plurality of times before the interior of the treatment furnace is cooled.

According to the refining method of the present invention, in the case of unused carbon parts used for producing polycrystalline silicon, after the chlorine circulation treatment in a high temperature state, the carbon parts are put in a depressurized state and a pressurized state by chlorine gas, The impurities can be removed in a short period of time without performing a heat treatment for a long time, and the productivity of the carbon parts processing can be improved.

Further, in the case of the used carbon parts, the silicon can be efficiently evaporated and removed without carrying out the depressurization treatment and the pressurization treatment with the chlorine gas in the high temperature state, without carving out the silicon for each carbon member. Thereby, there is no possibility that the strength of the carbon part is lowered because the carbon is not carved, and stable polycrystalline silicon can be produced.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, one embodiment of a method for purifying a carbon part according to the present invention will be described with reference to the drawings.

Fig. 1 shows an example of a purification apparatus used for carrying out this purification method. Reference numeral 1 denotes a processing line. As shown in Figs. 2 to 4, the processing furnace 1 is provided with a bottom wall 21, an upper wall 22, a front wall 23, a rear wall 24, and a side wall 25 in a box shape of a hexahedron And a door 26 that can be freely opened and closed is formed on the front wall 23 thereof. The inside of the processing furnace 1 is provided with a heater 27 in a planar shape along the inner wall surfaces of the rear wall 24 and the both side walls 25. By adjusting the current of the heater 27, And the temperature is adjusted. The walls 21 to 25 and the door 26 of the treatment furnace 1 are of a jacket structure so as to allow the cooling fluid to flow into the inner space 28. Reference numerals 29 to 31 denote cooling fluid supply pipes , And reference numerals 32 to 34 denote cooling fluid discharge pipes. A gas supply pipe 35 for introducing an inert gas or a chlorine gas to the inside is formed in the rear wall 24 of the processing furnace 1 and a gas discharge pipe 36 for discharging the internal gas is formed in the bottom wall 21, As shown in Fig. Reference numeral 37 denotes a nozzle portion passing through the electrode 38 of the heater 27. Reference numeral 39 is an observation window formed in the door. Reference numeral 40 denotes a heat insulating material made of graphite disposed inside each of the walls 21 to 25, and a heat insulating material 41 is detachably formed on the inside of the door 26 as well. The inert gas refers to argon gas, helium gas, and nitrogen gas.

The chlorine gas supply system 4 and the nitrogen gas supply system 5 are connected via the valves 6 to 8 to the purge line 9 for exhaust and the vacuum The line 10 is connected via the valves 11 and 12 in the same manner. In this case, the chlorine gas supply system 4 is composed of two systems, a small capacity line 13 having a small opening degree of the valve 6, and a large capacity line 14 having a large opening degree of the valve 7. Flow meters 13a, 14a and 5a are formed in the supply systems 4 and 5, respectively. The purge line 9 and the evacuated line 10 are connected to the scrubber 15, respectively. The vacuum line 10 is provided with a vacuum pump 16 such as a water seal pump. Reference numeral 17 denotes a safety mechanism which is operated by the pressure in the furnace. Reference numeral 19 in Fig. 1 denotes a control device for controlling the heater, each valve, etc., based on a preset program Fig. Reference numeral 2 denotes a cooling water supply system, and reference numeral 3 denotes a cooling water discharge system.

Next, a method for purifying a carbon part using the purifier thus configured will be described.

Fig. 5 shows a carbon part accommodated in the treatment furnace 1. 5A shows a state in which a carbon part 43 scattered in a nut shape or a cap shape is placed in a housing box 42 constructed by a plurality of carbon plates 41 or the like. (1). 5B shows a state in which rod-shaped carbon parts 44 such as heaters are stacked, and the carbon parts 44 are accommodated in the processing furnace 1 in a stacked state. In the purification of this carbon part, there are two methods, that is, the purification of the carbon part of the empty product and the purification of the used carbon part which has already been used for the production of the polycrystalline silicon. Fig. 6 is a chart showing temperature trends and the like in the processing furnace when purifying unused carbon parts, and Fig. 7 is a flowchart showing the processing in Fig. 6 in order. Fig. 8 is a chart showing temperature trends in the processing furnace in the pretreatment for purifying the used carbon parts, and Fig. 9 is a flowchart showing the processing in Fig. 8 in order.

First, the case of refining unused carbon parts will be described. This process can be largely divided into a drying process, a purification process, and a cooling process.

Drying process

The carbon parts are accommodated in the processing furnace 1 and the valve 8 of the nitrogen gas supply system 5 and the valve 11 of the purge line 9 are opened to supply nitrogen gas into the processing furnace 1, The temperature of the furnace is raised from 350 ° C. to 600 ° C., preferably from 400 ° C. to 550 ° C. to raise the temperature of the heater so as to dry the carbon parts (step 1). If the drying temperature is lower than 350 占 폚, water tends to remain in the treatment furnace 1 or in the carbon part, and if it exceeds 600 占 폚, energy loss is large. The nitrogen is supplied at a flow rate of, for example, 3 m 3 / hour to the volume of 1.2 m 3 in the treatment furnace 1 for about 1 hour to remove water from the carbon parts. Preferably, the flow rate (F: m 3 / h) is 1.5 times or more and 4.0 times or less the volume (m 3) in the treatment furnace 1.

Purification process

Next, the valve 8 of the nitrogen gas supply system 5 is closed and the valve 6 of the small capacity line 13 of the chlorine gas supply system 4 is opened, And the chlorine gas is flowed at a flow rate of 1 liter / minute (Step 2: chlorine distribution processing). At this time, the current of the heater is further raised to the heating state, and after about 3 hours, the purification of the carbon parts proceeds in a state in which the furnace temperature is stable. At this time, the internal temperature of the furnace is raised to a purifying temperature of 700 ° C or more and 1400 ° C or less, preferably 850 ° C or more and 1300 ° C or less. If the refining temperature is lower than 700 캜, the efficiency of removing impurities becomes lower. If the refining temperature is higher than 1400 캜, the reactor is liable to be damaged. In the purification process, the flow rate (F: m3 / hour) of the chlorine gas is preferably 0.1 times or more and 0.5 times or less the volume (m3) in the treatment furnace 1.

Next, both the valves 6 and 11 of the chlorine gas supply system 4 and the purge line 9 are closed with the chlorine gas in the processing furnace 1, and the valves of the vacuum line 10 (12) is opened to operate the vacuum pump (16), thereby evacuating the inside of the processing furnace (1) to reduce the pressure (step 3; As a result, chlorine gas contained in the treatment furnace 1 and chloride of impurities generated by reaction with the chlorine gas are discharged from the treatment furnace 1. When the processing furnace 1 reaches, for example, -0.09 MPa (G) (G indicates gauge pressure) as compared with the atmospheric pressure, the valve 12 of the evacuation line 10 is closed, 1) for 30 minutes, for example, in a reduced pressure state (step 4: reduced pressure holding process). The reduced pressure holding treatment is preferably carried out at a pressure of -0.02 MPa (G) or less and a pressure of -0.1 MPa (G) or more, preferably -0.05 MPa (G) Do. If the pressure in the treatment furnace is within the above range, impurities can be emitted from the carbon parts.

Next, while introducing the chlorine gas into the treatment furnace 1 by opening the valve 7 of the large capacity line 14 of the chlorine gas supply system 4, the inside of the treatment furnace 1 is compared with, for example, atmospheric pressure And pressurized until the pressure becomes about 0.01 MPa (G) (Step 5: chlorine pressurization). By allowing the inside of the treatment furnace 1 to be pressurized for about 30 minutes, chlorine gas permeates into the carbon parts to react with impurities in the carbon parts. The chlorine pressurizing treatment is more preferably 0.02 MPa (G) or more and 0.05 MPa (G) or less by pressurizing the inside of the treatment furnace to a pressure of 0.01 MPa (G) or more and 0.05 MPa (G) or less in comparison with the atmospheric pressure. If the pressure in the treatment furnace is 0.01 MPa (G) or more, the atmosphere does not become a negative pressure, and if the pressure is 0.05 MPa (G) or less, chlorine gas does not leak well.

Thereafter, the pressure reduction process is performed in which the vacuum pump 16 is operated by opening the valve 12 of the vacuumization line 10 to decompress the inside of the treatment furnace 1 to -0.09 MPa (G) The chlorine pressurizing treatment is carried out by pressurizing the inside of the treatment furnace 1 with chlorine gas at a pressure of 0.01 MPa (G) compared with the atmospheric pressure (steps 3 to 5).

That is, this refinement step is a step of refining the chlorine gas (step 2) for circulating the chlorine gas in the treatment furnace 1, the decompression treatment (step 3) for evacuating and decompressing the chlorine gas, (Step 4) in which chlorine gas is introduced from the reduced pressure state to pressurize the inside of the treatment furnace 1 to 0.01 MPa (G) (Step 5 ) Repeat steps 3 to 5 as many times as necessary. The number of repetition is determined depending on the size of the carbon part and the like. The number of iterations is twice in the case of small parts such as a bolt type and a nut type, and about four times in the case of a relatively large part like a heater.

If the processing is repeated a plurality of times, the process proceeds to the next cooling step.

Cooling process

In the cooling step, the small-capacity line 13 of the chlorine gas supply system 4 and the valves 6 and 11 of the purge line 9 are opened to introduce chlorine gas into the processing furnace 1 having a volume of 1.2 m 3, for example, 1 Liter, and cooled for 2 hours (Step 6: chlorine distribution treatment) while flowing at a flow rate of 1 liter / minute. Thereafter, the valve 6 of the chlorine gas supply system 4 is closed and the valve 8 of the nitrogen gas supply system 5 is opened to supply nitrogen gas at a flow rate of 3.5 m < 3 > / hour, for example, M < 3 > in the processing furnace 1, and the inside of the processing furnace 1 is cooled from the chlorine gas atmosphere to the nitrogen gas atmosphere while cooling to room temperature (step 7; nitrogen circulation treatment). In the cooling step, the flow rate of the chlorine gas (F: 3 m 3 / hour) is preferably 0.02 times or more and 0.1 times or less the volume (m 3) in the treatment furnace 1. In the cooling step, the flow rate (F: m3 / hour) of the inert gas is preferably 2.0 times or more and 5.0 times or less the volume (m3) in the treatment furnace 1.

By such a series of treatments, impurities such as boron and phosphorus in the carbon parts are removed and purified as high purity carbon. In short, this refining method is a method of purifying an impurity element in a carbon part by reacting with the chlorine gas and discharging the chlorine gas, and by alternately repeating the reaction with the chlorine gas and the maintenance of the reduced pressure state, It is possible to sufficiently react with the impurities therein to remove it.

Next, a description will be given of a method for purifying a used carbon part which has been provided for the production of polycrystalline silicon.

The used carbon part has polycrystalline silicon adhered to its surface with the production of the polycrystalline silicon. For this reason, a pretreatment for removing silicon deposits on the surface is performed first, and thereafter, the same treatment as that for the above-described unused carbon parts is performed. The process for removing the deposit is divided into a drying process, an adherend removal and purification process, and a cooling process.

Drying process

The carbon parts are accommodated in the processing furnace 1 and the valve 8 of the nitrogen gas supply system 5 and the valve 11 of the purge line 9 are opened to introduce nitrogen gas into the processing furnace 1 having a volume of 1.2 m 3 The inside of the furnace is heated while the furnace is being supplied (step 21: drying treatment for used carbon). For example, at a flow rate of about 2 m < 3 > / hour for about 90 minutes, thereby removing moisture in the carbon parts. The temperature is raised to the silicon removal temperature. The silicon removal temperature is about 350 DEG C or more and about 600 DEG C or less, preferably 400 DEG C or more and 550 DEG C or less. When the drying temperature is lower than 350 ° C, moisture tends to remain. When the drying temperature exceeds 600 ° C, silicon tends to precipitate. In the drying step, the flow rate (F: m3 / hour) of the inert gas is preferably 1.5 times or more and 4.0 times or less the volume (m3) in the treatment furnace 1.

Removal and purification process

Both the valves 8 and 11 of the nitrogen gas supply system 5 and the purge line 9 are closed and the valve 12 of the vacuum line 10 is closed from the state in which the nitrogen gas is circulated in the processing furnace 1, And the vacuum pump 16 is operated to evacuate the inside of the treatment furnace 1 to reduce the pressure (Step 22: decompression treatment for used carbon). In this case also, the valve 12 of the evacuation line 10 is closed when the processing furnace 1 reaches the reduced pressure state of -0.09 MPa (G) as compared with the atmospheric pressure. (G) or less and -0.1 MPa (G) or more and -0.1 MPa (G) or less and -0.1 MPa (G) or less in the used pressure reducing treatment for carbon, ) Or more. If the pressure in the treatment furnace is within the above range, impurities can be emitted from the carbon parts.

Next, the valve 6 or 7 of any line 13 or 14 of the chlorine gas supply system 4 is opened to introduce chlorine gas into the treatment furnace 1 (step 23: chlorine pressurization for carbon used process). When the inside of the treatment furnace 1 is about 0.01 MPa (G), for example, as compared with the atmospheric pressure, the valve 6 or 7 is closed to put the chlorine gas in the treatment furnace 1 ; Pressure holding treatment). In the pressurized holding treatment, it is more preferable that the inside of the treatment furnace is pressurized to about 0.01 MPa (G) or more and about 0.05 MPa (G) or less and 0.02 MPa (G) or more and 0.05 MPa (G) or less, If the pressure in the treatment furnace is 0.01 MPa (G) or more, the atmosphere does not become negative, and if the pressure is 0.05 MPa (G) or less, chlorine gas does not leak well. In this state, for example, 90 minutes is maintained, chlorine gas is permeated into the carbon part, and the silicon deposit is reacted with chlorine gas to make silicon tetrachloride. The silicon tetrachloride has a boiling point of 57 ° C. Then, the opening and closing of the valve is switched, and the evacuation and the introduction of the chlorine gas are alternately repeated a necessary number of times, for example, twice according to the amount of the deposit (steps 22 to 24).

Cooling process

In the cooling step, the opening and closing of the valve is switched to open the valve 8 of the nitrogen gas supply system 5 to introduce nitrogen gas into the treatment furnace 1 having a volume of 1.2 m 3 at a flow rate of, for example, 3.5 m 3 / , And the inside of the treatment furnace 1 is cooled to room temperature while replacing the inside of the furnace 1 from the chlorine gas atmosphere to the nitrogen gas atmosphere (step 25). The cooling time is about 60 minutes. In the cooling step, preferably, the flow rate (F: m3 / hour) of the chlorine gas is 2.0 times or more and 5.0 times or less the volume (m3) in the treatment furnace 1.

After the series of processes of the drying process, the deposit removing process, and the cooling process, a series of heat treatment including a drying process, a refining process, and a cooling process is performed by the same method shown in FIG. 6, which is applied to the unused carbon parts. In this case, the number of repetitions of the respective processes of the decompression process, the decompression maintenance process, and the chlorine pressure process in the purification process is four. Fig. 10 is a flowchart showing a case in which the process in the pattern shown in Fig. 8 and the process in the pattern shown in Fig. 6 are successively performed on the used carbon parts.

When the carbon parts are taken out from the treatment furnace 1 after the treatment as described above, most of the deposited silicon becomes silicon tetrachloride and disappears. Since the remaining silicon deposits are also separated from the carbon parts, they can be easily removed have. In addition, the inside impurities are removed and regenerated as high purity carbon parts.

The unused and used carbon parts subjected to such treatment are used to precipitate polycrystalline silicon in a Siemens type reaction (the same specifications of A to D in each reaction and in the same reaction conditions) Table 1 shows the results. The polycrystalline silicon can have a resistivity of 3000 to 4000? Cm, a phosphorus concentration of 0.02 to 0.03 ppba, and a boron concentration of 0.006 to 0.007 ppba. Regarding the unused carbon parts, the repetition number of the decompression processing (step 3), the decompression maintenance processing (step 4), and the chlorine pressurization processing (step 5) were performed twice by processing using the pattern shown in Fig. The total treatment time was about 8.5 hours. The used carbon parts are subjected to a pressure reducing treatment (step 22) for carbon used by the treatment with the pattern shown in Fig. 8, a chlorine pressing treatment (step 23) for carbon used, a pressure holding treatment The number of repetition times of the pressure reducing treatment (step 4) and the chlorine pressurizing treatment (step 5) was four times by the repetition number of times . The total treatment time was about 17.7 hours. The numerical values in parentheses in each reactor in Table 1 represent the number of batches of each polycrystalline silicon reaction, and the respective values of the resistivity, phosphorus concentration and boron concentration represent the average value of the batch.

On the other hand, as a comparative example, a treatment with a chlorine gas flow is carried out on a carbon part of an article of non-refuse as shown in Japanese Patent Publication No. 2649166 by using a gas flow type treatment furnace by heating an outer tube heater using a quartz tube. Using this unused carbon component, polysilicon was precipitated from E by a Siemens type reaction. Table 1 also shows the resistivity values, the results of boron and phosphorus concentration after polycrystalline silicon deposition using the treated carbon parts. In the comparative example, a quartz tube having a diameter of 100 mm and a length of 2 m was used, and the heater setting temperature was about 900 占 폚. The treatment method was chlorine gas treatment (8 hours), nitrogen gas treatment, chlorine gas treatment (8 hours), and nitrogen gas treatment.

In the case of the embodiment, the processing time required for the number of repetitions is shown in Table 2. The processing time is an integrated value of time for each processing shown in Fig. 6 or Fig.

Table 3 shows the results of confirming the refining effect of the used carbon parts with or without the chlorine circulation treatment or the number of repetitions thereof by the resistivity. In this case, the treatment temperature is about 500 캜, and the removal treatment time is about 2.5 hours / s.

From these results, it can be seen that, in the purification method of the present invention, a high-purity carbon component can be obtained in a short time. Regarding the number of times of repetition of processing, it is preferable that at least two times of the decompression treatment, the decompression holding treatment and the chlorine pressurization treatment are performed for the unused carbon parts, and the used carbon The pressure reducing treatment for use, the chlorine pressurizing treatment for used carbon, and the pressurizing holding treatment are performed twice, and the subsequent processes using the pattern shown in Fig. 6 are subjected to the decompression treatment, the decompression holding treatment and the chlorine pressurizing treatment.

The present invention is not limited to the above-described embodiment, and various modifications may be added within the scope of the present invention.

For example, in the above embodiment, nitrogen gas is used in the gas replacement and drying process in the treatment furnace, but an inert gas other than the nitrogen gas may be used. In addition, the chlorine gas supply system has two systems of the small capacity line and the large capacity line, but the flow rate may be adjusted by one system. When the used carbon parts are to be treated, the processing according to the processing pattern shown in Fig. 6 is performed after the completion of the processing pattern shown in Fig. 8. However, after the processing shown in Fig. 8, In this case, the cooling step shown in Fig. 8 and the drying step shown in Fig. 6 may be omitted.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a piping diagram showing an example of a purification apparatus used for carrying out a purification method of a carbon part according to the present invention. Fig.

Fig. 2 is a front view of the processing furnace in the refining apparatus of Fig. 1; Fig.

Fig. 3 is a top view of the process of Fig. 2; Fig.

Fig. 4 is a side view of the process of Fig. 2; Fig.

5A and 5B are perspective views showing examples of carbon parts accommodated in the processing furnace of FIG. 2. FIG. 5A shows a state in which scattered carbon parts are placed in a box, and FIG. 5B shows a state in which rod-shaped carbon parts are stacked .

6 is a chart showing a temperature trend in a treatment furnace and the like in one embodiment of a method for purifying a carbon part according to the present invention.

Fig. 7 is a flowchart showing the processing in Fig. 6 in order. Fig.

Fig. 8 is a chart showing the temperature trend in the treatment furnace during pretreatment in one embodiment of the method for purifying the used carbon parts; Fig.

Fig. 9 is a flowchart showing the processing in Fig. 8 in order. Fig.

Fig. 10 is a flowchart showing a series of processes in the order of an embodiment of a method for purifying a used carbon part. Fig.

[Description of Drawings]

1 processing line

2 Cooling water supply system

3 Coolant discharge meter

4 Chlorine gas supply system

5 Nitrogen gas supply system

6 to 8 valves

9 Fuzzy line

10 Vacuumization line

11 and 12 valves

13 Small capacity line

14 large capacity line

15 Scrubber

16 Vacuum pump

17 Differential pressure gauge

18 Safety equipment

19 control circuit

21 floor wall

22 Upper wall

23 front wall

24 rear wall

25 side wall

26 doors

27 Heater

28 interior space

29 ~ 31 Cooling fluid supply pipe

32 ~ 34 Cooling fluid discharge tube

35 gas supply pipe

36 gas discharge pipe

37 nozzle section

38 electrode

39 Observation window

41 carbon plate

42 receptacle

43, 44 Carbon parts

Claims (14)

A method for purifying a carbon component for producing polycrystalline silicon, A process of accommodating the carbon part in the treatment furnace and replacing the inside of the treatment furnace with an inert gas, A drying treatment for raising the inner temperature to the drying temperature and circulating an inert gas to dry the carbon parts, A chlorine circulation treatment for raising the temperature of the treatment furnace to a refining temperature higher than the drying temperature after the drying treatment and for circulating chlorine gas in the treatment furnace, A decompression process for decompressing the interior of the apparatus after the chlorination process, A pressure reduction maintaining process for maintaining the inside of the process furnace under the pressure reducing condition caused by the pressure reducing process, A chlorine pressurizing treatment for introducing chlorine gas into the treatment furnace after the reduced pressure holding treatment to pressurize the inside of the treatment furnace, and And a treatment for cooling the inside of the treatment furnace after the chlorine pressurization treatment. The method according to claim 1, Wherein the decompression maintaining treatment is performed so that the inside of the treatment furnace is kept at -0.02 MPa (G) or less and -0.1 MPa (G) or more compared with the atmospheric pressure. 3. The method according to claim 1 or 2, Wherein the chlorine pressurizing treatment pressurizes the interior of the treatment furnace to not less than 0.01 MPa (G) and not more than 0.05 MPa (G), as compared with the atmospheric pressure. 3. The method according to claim 1 or 2, Wherein the drying temperature is higher than or equal to 350 ° C and lower than or equal to 600 ° C, and the purifying temperature is higher than or equal to 700 ° C and lower than or equal to 1400 ° C. 3. The method according to claim 1 or 2, Wherein the inside of the treatment furnace is cooled after the steps from the decompression treatment to the chlorine pressure treatment are repeated a plurality of times. A method of purifying a carbon part after it has been used in the production of polycrystalline silicon, A process in which the used carbon parts used in the production of the polycrystalline silicon are accommodated in the processing furnace and the inside of the processing furnace is replaced with an inert gas, A drying treatment for the carbon used to dry the used carbon parts by raising the temperature to the silicon removal temperature while passing the inert gas through the treatment furnace, A used carbon decompression treatment for decompressing the inside of the treatment furnace after the drying treatment for the used carbon, A used chlorine pressurizing treatment for introducing chlorine gas into the treatment furnace after the decompression treatment for the used carbon, A pressurizing and holding treatment for keeping the inside of the treatment furnace in a pressurized state by the chlorine gas after the pressurizing treatment of the used carbon for chlorination, A chlorine circulation process for raising the temperature of the inside of the treatment furnace to the purification temperature after the pressure holding treatment and circulating chlorine gas in the treatment furnace, A decompression process for decompressing the interior of the apparatus after the chlorination process, A pressure reduction maintaining process for maintaining the inside of the process furnace under the pressure reducing condition caused by the pressure reducing process, A chlorine pressurizing treatment for introducing chlorine gas into the treatment furnace after the reduced pressure holding treatment to pressurize the inside of the treatment furnace, and And a treatment for cooling the inside of the treatment furnace after the chlorine pressurization treatment. The method according to claim 6, Wherein the used carbon reduced-pressure treatment is maintained at -0.02 MPa (G) or less and -0.1 MPa (G) or more in comparison with the atmospheric pressure in the treatment furnace. 8. The method according to claim 6 or 7, Wherein the pressurization maintaining treatment pressurizes the inside of the treatment furnace to not less than 0.01 MPa (G) and not more than 0.05 MPa (G), as compared with the atmospheric pressure. 8. The method according to claim 6 or 7, Wherein the silicon removal temperature is 350 DEG C or more and 600 DEG C or less. 8. The method according to claim 6 or 7, Wherein the refining temperature is 700 DEG C or more and 1400 DEG C or less. 8. The method according to claim 6 or 7, Wherein the step of repeating the steps from the decompression treatment for the carbon to the pressurization and holding treatment is repeated a plurality of times before the transition to the chlorine circulation treatment. 8. The method according to claim 6 or 7, A cooling step and a drying step during the transition from the pressure holding treatment to the chlorine circulation treatment, In the cooling step, the inside of the treatment furnace is cooled, In the drying step, the inside of the treatment furnace is heated to a drying temperature, and an inert gas is circulated to dry the carbon parts. 13. The method of claim 12, Wherein the drying temperature is 350 DEG C or more and 600 DEG C or less. 8. The method according to claim 6 or 7, Wherein the inside of the treatment furnace is cooled after the steps from the decompression treatment to the chlorine pressure treatment are repeated a plurality of times.

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